Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

INTRODUCTION

Low back pain affects 80% of the population with half of cases attributed to intervertebral disc (IVD) degeneration. However, the majority of treatments focus on pain management, with none targeting the underlying pathophysiological causes. PCRX-201 presents a novel gene therapy approach that addresses this issue. PCRX-201 codes for interleukin-1 receptor antagonist (IL-1Ra), the natural inhibitor of the pro-inflammatory cytokine IL-1, which orchestrates the catabolic degeneration of the IVD. Here, we investigated the ability of PCRX-201 to transduce human nucleus pulposus (NP) cells in vitro to increase production and release of IL-1Ra and assess downstream effects on cytokine and catabolic enzyme production.

METHODS

Degenerate human NP cells (monolayer n=7, 3D alginate n=6) and tissue explants (n=5) were transduced with PCRX-201 at 0,750 or 3000 multiplicities of infection (MOI) and cultured for 5, 21 and 14 days, respectively. Cell culture supernatant was collected throughout the culture duration and downstream targets associated with pain and degeneration (IL-1β, IL-6, IL-8, MMP3, ADAMTS4, and VEGF) were assessed using ELISA. The effects of PCRX-201 transduction on anabolic and catabolic protein expression within human IVD explant tissue was assessed using immunohistochemistry.

RESULTS

PCRX-201 showed no adverse effects on NP cell viability. IL-1Ra production was increased in monolayer and 3D-cultured NP cells and tissue infected with PCRX-201. The production of downstream catabolic proteins such as IL-1β, IL-6, MMP3, ADAMTS4 and VEGF was decreased in both 3D-cultured NP cells (Figure 1) and tissue explants. The cellular expression of IL-1Ra and aggrecan was increased, whereas expression of catabolic factors (IL-1β, MMP3, VEGF) was decreased in ex vivo human NP explant tissue following PCRX-201 transduction.

DISCUSSION

Here, we have demonstrated that a novel gene therapy, PCRX-201, is able to transduce and increase the production of IL-1Ra in degenerate NP cells in vitro and within ex vivo human NP tissue explants. In 3D culture and tissue explants, the increased production of IL-1Ra also resulted in a decrease in the production of IL-1β, IL-6, MMP3, ADAMTS4, and VEGF. As these pro-inflammatory and catabolic factors are all thought to contribute to and exacerbate IVD degeneration, these results suggest that PCRX-201-driven production of IL-1Ra in NP cells and tissue enables the inhibition of IL-1β-driven catabolism during IVD degeneration. At present, no treatments for IVD degeneration target the underlying cellular causes. The ability of PCRX-201 to elicit anti-inflammatory and anti-catabolic responses in degenerate NP cells and tissue is promising and warrants further investigation in vitro and in vivo, to determine the efficacy of this promising, novel gene therapy. Furthermore, given some of the shared underlying aetiology with OA, the effects shown here may also have favourable implications for the on-going clinical work with PCRX-201 in knee OA.

Figure 1. (a) IL-1Ra, (b) IL-1β, (c) IL-6, (d) IL-8, (e) MMP3, (f) ADAMTS4, and (g) VEGF production in cell culture supernatant (ELISA) after 21 days post PCRX-201 infection in 3D human NP cell culture, ± 7 days 10 ng/mL IL-1β stimulation. Statistical analysis was performed using Kruskal-Wallis tests with post hoc analysis, p ≤ 0.05.